The most familiar data recording system used in logging applications is the telephone message recorder. In such a system, a voice activated relay responds to a message signal to activate a motor which moves a tape of a magnetic tape cartridge in a familiar manner. A control circuit is operative to provide play, rewind and other discretionary features as is also familiar with such machines. The control circuit is operative to disengage the voice actuated relay to prevent recording while any of the play, rewind, or any other feature is operative.
Another familiar data logging system is one which is used in computer installations. In this application, open reels of magnetic tape are used rather than cartridges. Reels of this type, although large and capable of storing large amounts of information, require significant amounts of handling and are not as simple and carefree as cartridge systems.
The trade-off, which exists at present, is to use a simple, low cost, low storage capacity cartridge or a labor intensive, high cost open reel system. The constraints imposed on such a system by the application for which the system is designed are worth considering to determine just how a decision is made as to what type of system is to be used.
Consider a high end data monitoring or logging system such as might be used for military applications. Such a system operates under quite strict requirements. A first requirement is that if any data input occurs, it must be collected as it occurs. That is, it must be collected in real time. Another requirement of the system is that no data be lost if the recorder is on line and in a quiescent state when the flow of data commences. A corollary of this latter requirement is that the recorder system operates at a data rate significantly higher than that of the source data rate. Such requirements are not met by available prior art recording systems of the type described above.